1. Field of the Invention
The present invention relates generally to a ceramic electronic component in which electrodes are formed so as to make contact with a functional ceramic thin film and a method of fabricating the same, and more particularly, to a ceramic electronic component in which electrodes contacting a ceramic thin film are improved and a method of fabricating the same.
2. Description of the Prior Art
In fabricating an electronic component having a functional ceramic thin film which is crystalline, attempts have been made in recent years to form a functional ceramic thin film in a deposited state on a substrate so as to simplify the structure of the component. Thus, when the ceramic thin film which is crystalline is formed in a film deposited state, a substrate on which the thin film is formed must be heated in a predetermined atmosphere of film formation.
On the other hand, in taking out its function, for example, electrical properties from the functional ceramic thin film, electrodes must be formed in such a manner as to make contact with the ceramic thin film. Consequently, it is necessary that thin film electrodes are formed on a substrate and then, a functional ceramic thin film which is crystalline is formed in a film deposited state on the thin film electrodes. In such a case, while the functional ceramic thin film is being formed, the thin film electrodes themselves formed beneath the ceramic thin film are also exposed to high temperature. Accordingly, as an electrode material used for this type of application, one superior in stability at high temperature is required.
Furthermore, a functional ceramic thin film having a thickness of several .mu.m may react with thin film electrodes having a thickness of submicrons while the ceramic thin film is being formed, to degrade the functionality of the ceramic thin film. Consequently, it is also necessary to select an electrode material substantially low in reactivity with the ceramic thin film.
Additionally, when a functional ceramic thin film made of an oxide or a complex oxide material is formed, it is necessary to introduce an oxygen gas at the same time of film formation. Therefore, it is needed to use an electrode material not only superior in stability at high temperature and low in reactivity with the ceramic thin film but also superior in oxidation-resistance property at high temperature.
Since the above described electrode material is made to function as an electrode, it is naturally essential that its electrical conductivity is held good.
As electrode materials superior in oxidation-resistance property at high temperature, Pt, Au, Ta, Ti and the like have been conventionally used.
A PbTiO.sub.3 film and a Pb(Zr, Ti)O.sub.3 film containing reaction active Pb are formed, for example, by sputtering on each of electrodes made of Pt, Au, Ta and Ti which have been conventionally known as electrode materials superior in oxidation-resistance property at high temperature, to examine suitability of Pt, Au, Ta and Ti as the electrode materials. The results of the examination are shown in Table 1.
TABLE 1 ______________________________________ oxidation reactivity resistance with electrode at high ceramic other material temperature thin film problems ______________________________________ Pt very good very low high cost Au good low high cost Ta fit for use high -- Ti good high -- ______________________________________
As obvious from Table 1, Pt and Au are superior in oxidation-resistance property at high temperature and low in reactivity with the ceramic thin film, while being very high in electrode cost.
Conversely, Ta and Ti are not too high in electrode cost, while being high in reactivity with the ceramic thin film and thus, cannot be used.